A semiconductor device serving as an electronic device to be mounted on an electronic equipment or the like is generally subjected to a test for eliminating potential defects therein by using an Integrated Circuit socket (IC socket) at a stage before the semiconductor device is mounted. As shown in PATENT DOCUMENT 1, for example, such an IC socket is provided on a printed wiring board (a test board or a mounting board).
In the case where a semiconductor device socket is provided in a transmission line that transmits an RF (radio frequency) signal in a relatively high frequency band such as 1 GHz or above, there has been known a technique for enhancing a transmission performance of a signal in a relatively high frequency band by subjecting an IC socket to impedance matching in order to enhance the transmission performance of the signal in the relative high frequency band, and decreasing inductance by further reducing a length between a contact portion of a movable terminal portion of a contact terminal and a proximal end portion of a solder fixation terminal portion thereof.
As shown in PATENT DOCUMENT 1, for example, a contact probe serving as the contact terminal is disposed in an insertion hole in a metal block of the IC socket to be disposed on the wiring board.
Such an IC socket comprises, as its main elements: the metal block fixed to a surface of a wiring board through an insulating board made of a resin; a guide plate stacked on an upper end portion of the metal block through another insulating board made of a resin; and a plurality of contact probes.
Among the plurality of contact probes, an RF signal contact probe is fixed in such a way as to define a hollow portion that forms an air layer between an outer peripheral portion of the probe and the insertion hole in the metal block mentioned above, and is configured to form a so-called coaxial probe that the contact probe is adopted as a central conductor and an inner wall of the insertion hole is adopted as an external conductor. Hereby, impedance matching is achieved. However, a portion of each insulating board into which each plunger of the RF signal contact probe is to be inserted is not formed into the coaxial probe. Moreover, among the plurality of contact probes, a power supply contact probe is covered with a dielectric tube around an outer peripheral portion of a barrel thereof. Herewith, a metal pipe of the power supply contact probe is insulated from the inner wall of the insertion hole in the metal block. Furthermore, among the plurality of contact probes, a grounding contact probe is arranged such that an outer peripheral portion of a metal pipe thereof comes into contact with the inner wall of the insertion hole in the metal block.
And then, as disclosed in PATENT DOCUMENT 2, for example, there has been proposed a technique to provide an annular dielectric body for slidably supporting each of an upper plunger and a lower plunger at each open end portion of an insertion hole of a base from which each of the upper plunger and the lower plunger projects, in order to achieve the impedance matching with respect to a portion between a base of a socket and each of the upper plunger and the lower plunger projecting from the barrel of the signal probe in the PATENT DOCUMENT 1 described above, such that the portion does not form the coaxial probe and hence causes impedance mismatching. The dielectric body has a support hole which is located at a central part and each of the upper plunger and the lower plunger can slide.